Thermodynamic properties and corrosivity of a new absorption heat pump working pair: Lithium nitrate + 1-butyl-3- methylimidazolium bromide + water

LiNO3-[BMIM]Br/H2O ternary system has been proposed as a new absorption working pair to improve the shortcomings of high crystallization temperature for LiNO3/H2O and high viscosity for [BMIM]Br/H2O working pairs. The crystallization temperature, vapor pressure, density, viscosity, specific heat capacity, and dissolution enthalpy of this ternary system at a mass ratio of 2:1 (LiNO3 to [BMIM]Br) were measured. The specific enthalpy was calculated based on the measured specific heat capacity and dissolution enthalpy. Regression equations for these thermodynamic properties were obtained by a least-squares method. Results showed that LiNO3-[BMIM]Br/H2O had nearly identical vapor pressure with that for LiNO3/H2O at a 10% lower mass concentration. Meanwhile, under the same absorption ability, LiNO3-[BMIM]Br/H2O had much lower crystallization temperature than LiNO3/H2O, and much lower viscosity than [BMIM]Br/H2O. At the temperature below 587.75 K, LiNO3-[BMIM]Br/H2O has a reliable thermal stability. The corrosivity of LiNO3-[BMIM]Br/H2O to carbon steel and copper was larger than that of LiNO3/H2O, while obviously less than that of LiBr/H2O. As an alternative working pair, LiNO3-[BMIM]Br/H2O shows a great potential in absorption heat pump, especially at high temperature.